The invention relates generally to heart rate analyzers and more particularly to a heart rate analyzer for monitoring the rate of heartbeating and for providing a visual indication of at least either the maximum or the minimum heart rate within a predetermined unit of time.
A variety of heart rate or heartbeat rate monitors and/or analyzers are known in the prior art. One type of heart rate monitor, typified by U.S. Pats. Nos. 3,948,250 and 4,083,366, compares a measured heart rate with predetermined high and low heart rate limits for the purpose of sounding an alarm if such limits are exceeded. Moreover, the average heart rate may be continually or periodically displayed.
U.S. Pat. No. 3,893,453 discloses still another type of heart rate monitor in which an average heart rate is periodically printed or scribed on a calibrated scale, as for instance ECG chart or graph paper, to show trends or changes in the heartbeat rate over a relatively long period of time. Such formating of the heat rate indications is normally termed trending for its ability to reveal, at a glance, a history of heartbeat rate changes over some relatively long period of time.
More recently, the devloping techniques of ambulatory cardiography, or Holter Cardiography as it is more commonly known, have given rise to relatively sophisticated scanners and analyzers which are utilized for scanning and analyzing tapes having ECG signals recorded therein in real time and played back at a greatly accelerated rate, i.e., 120 times speed at which recorded. These systems, typified by the American Optical Scanner Models 6002 and 6004 for Holter Cardiography, particularly Option Two thereto, marketed by American Optical Corporation, provided a sequential heart rate trend display in which the average heart rate was graphically recorded on a strip chart at one-minute intervals. A continuous record of the average heart rate is disclosed in the Holter-type scanner of U.S. Pat. No. 4,073,011. Still another Holter-type scanner of prior art has provided a bar-graph or histogram type of R-R interval display in which vertical bars indicative of some quantity of heartbeats at a particular average interval are arrayed side-by-side as a function of heart rate. Such trending of the heart rate may also be used by an analyst to facilitate retrieval, as from storage or record (as a strip chart), the particular ECG waveform(s) giving rise to the trend data.
While each of the aforementioned systems does provide some degree of insight into a patient's heart rate, the particular heart rate information displayed usually tends to be rather coarse and does not afford a closer analysis of heart rate excursions over relaively short intervals of time.
In addition to some of the more conventional information which may be gleaned by a physician through analysis of a histogram or other type of trend display showing a patient's heart rate, certain further information of particular significance might be obtained if the physician or operator is able to rapidly and accurately determine the occurrence of so-called "dropped beats". It is felt by some that a close relation exists between the occurrence of dropped or omitted heartbeats and the existence of second degree heart block. This latter condition is one which is relatively readily treatable by the installation of a pacemaker, and thus the detection of second degree AV heart block is particularly significant. The conventional Holter monitoring technique, in which an operator watches a rapidly displayed sequence of superimposed ECG complexes, has not lent itself to the easy detection of dropped beats by the operator, and the graphical recording of every ECG complex for later review consumes considerable time and paper, as well as still requiring a slow review by an analyst.
Accordingly, it is a principal object of the present invention to provide a heart rate analyzer which is capable of providing a visual indication of at least either the maximum or the minimum heart rate of a patient within a predetermined unit of time. Moreover, it is a further object to provide visual indications of both the maximum and the minimum heart rate within the predetermined unit of time.
A further object of the invention is the provision of visual indications of the maximum and minimum heart rates occurring within predetermined units of time of such duration that valuable information is readily retrievable.
It is a still further object of the present invention to determine the maximum and the minimum heart rates determined within a predetermined unit of time in a manner facilitating the identification and/or retrieval of "dropped beats" from the stored or recorded ECG waveforms.